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Diffstat (limited to '')
| -rw-r--r-- | src/pdkim/pdkim.c | 2057 |
1 files changed, 2057 insertions, 0 deletions
diff --git a/src/pdkim/pdkim.c b/src/pdkim/pdkim.c new file mode 100644 index 0000000..594af03 --- /dev/null +++ b/src/pdkim/pdkim.c @@ -0,0 +1,2057 @@ +/* + * PDKIM - a RFC4871 (DKIM) implementation + * + * Copyright (C) 2009 - 2016 Tom Kistner <tom@duncanthrax.net> + * Copyright (C) 2016 - 2018 Jeremy Harris <jgh@exim.org> + * + * http://duncanthrax.net/pdkim/ + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include "../exim.h" + + +#ifndef DISABLE_DKIM /* entire file */ + +#ifndef SUPPORT_TLS +# error Need SUPPORT_TLS for DKIM +#endif + +#include "crypt_ver.h" + +#ifdef SIGN_OPENSSL +# include <openssl/rsa.h> +# include <openssl/ssl.h> +# include <openssl/err.h> +#elif defined(SIGN_GNUTLS) +# include <gnutls/gnutls.h> +# include <gnutls/x509.h> +#endif + +#include "pdkim.h" +#include "signing.h" + +#define PDKIM_SIGNATURE_VERSION "1" +#define PDKIM_PUB_RECORD_VERSION US "DKIM1" + +#define PDKIM_MAX_HEADER_LEN 65536 +#define PDKIM_MAX_HEADERS 512 +#define PDKIM_MAX_BODY_LINE_LEN 16384 +#define PDKIM_DNS_TXT_MAX_NAMELEN 1024 + +/* -------------------------------------------------------------------------- */ +struct pdkim_stringlist { + uschar * value; + int tag; + void * next; +}; + +/* -------------------------------------------------------------------------- */ +/* A bunch of list constants */ +const uschar * pdkim_querymethods[] = { + US"dns/txt", + NULL +}; +const uschar * pdkim_canons[] = { + US"simple", + US"relaxed", + NULL +}; + +const pdkim_hashtype pdkim_hashes[] = { + { US"sha1", HASH_SHA1 }, + { US"sha256", HASH_SHA2_256 }, + { US"sha512", HASH_SHA2_512 } +}; + +const uschar * pdkim_keytypes[] = { + [KEYTYPE_RSA] = US"rsa", +#ifdef SIGN_HAVE_ED25519 + [KEYTYPE_ED25519] = US"ed25519", /* Works for 3.6.0 GnuTLS, OpenSSL 1.1.1 */ +#endif + +#ifdef notyet_EC_dkim_extensions /* https://tools.ietf.org/html/draft-srose-dkim-ecc-00 */ + US"eccp256", + US"eccp348", + US"ed448", +#endif +}; + +typedef struct pdkim_combined_canon_entry { + const uschar * str; + int canon_headers; + int canon_body; +} pdkim_combined_canon_entry; + +pdkim_combined_canon_entry pdkim_combined_canons[] = { + { US"simple/simple", PDKIM_CANON_SIMPLE, PDKIM_CANON_SIMPLE }, + { US"simple/relaxed", PDKIM_CANON_SIMPLE, PDKIM_CANON_RELAXED }, + { US"relaxed/simple", PDKIM_CANON_RELAXED, PDKIM_CANON_SIMPLE }, + { US"relaxed/relaxed", PDKIM_CANON_RELAXED, PDKIM_CANON_RELAXED }, + { US"simple", PDKIM_CANON_SIMPLE, PDKIM_CANON_SIMPLE }, + { US"relaxed", PDKIM_CANON_RELAXED, PDKIM_CANON_SIMPLE }, + { NULL, 0, 0 } +}; + + +static blob lineending = {.data = US"\r\n", .len = 2}; + +/* -------------------------------------------------------------------------- */ +uschar * +dkim_sig_to_a_tag(const pdkim_signature * sig) +{ +if ( sig->keytype < 0 || sig->keytype > nelem(pdkim_keytypes) + || sig->hashtype < 0 || sig->hashtype > nelem(pdkim_hashes)) + return US"err"; +return string_sprintf("%s-%s", + pdkim_keytypes[sig->keytype], pdkim_hashes[sig->hashtype].dkim_hashname); +} + + +int +pdkim_hashname_to_hashtype(const uschar * s, unsigned len) +{ +int i; +if (!len) len = Ustrlen(s); +for (i = 0; i < nelem(pdkim_hashes); i++) + if (Ustrncmp(s, pdkim_hashes[i].dkim_hashname, len) == 0) + return i; +return -1; +} + +void +pdkim_cstring_to_canons(const uschar * s, unsigned len, + int * canon_head, int * canon_body) +{ +int i; +if (!len) len = Ustrlen(s); +for (i = 0; pdkim_combined_canons[i].str; i++) + if ( Ustrncmp(s, pdkim_combined_canons[i].str, len) == 0 + && len == Ustrlen(pdkim_combined_canons[i].str)) + { + *canon_head = pdkim_combined_canons[i].canon_headers; + *canon_body = pdkim_combined_canons[i].canon_body; + break; + } +} + + + +const char * +pdkim_verify_status_str(int status) +{ +switch(status) + { + case PDKIM_VERIFY_NONE: return "PDKIM_VERIFY_NONE"; + case PDKIM_VERIFY_INVALID: return "PDKIM_VERIFY_INVALID"; + case PDKIM_VERIFY_FAIL: return "PDKIM_VERIFY_FAIL"; + case PDKIM_VERIFY_PASS: return "PDKIM_VERIFY_PASS"; + default: return "PDKIM_VERIFY_UNKNOWN"; + } +} + +const char * +pdkim_verify_ext_status_str(int ext_status) +{ +switch(ext_status) + { + case PDKIM_VERIFY_FAIL_BODY: return "PDKIM_VERIFY_FAIL_BODY"; + case PDKIM_VERIFY_FAIL_MESSAGE: return "PDKIM_VERIFY_FAIL_MESSAGE"; + case PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH: return "PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH"; + case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: return "PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE"; + case PDKIM_VERIFY_INVALID_BUFFER_SIZE: return "PDKIM_VERIFY_INVALID_BUFFER_SIZE"; + case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD: return "PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD"; + case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: return "PDKIM_VERIFY_INVALID_PUBKEY_IMPORT"; + case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR: return "PDKIM_VERIFY_INVALID_SIGNATURE_ERROR"; + case PDKIM_VERIFY_INVALID_DKIM_VERSION: return "PDKIM_VERIFY_INVALID_DKIM_VERSION"; + default: return "PDKIM_VERIFY_UNKNOWN"; + } +} + +const uschar * +pdkim_errstr(int status) +{ +switch(status) + { + case PDKIM_OK: return US"OK"; + case PDKIM_FAIL: return US"FAIL"; + case PDKIM_ERR_RSA_PRIVKEY: return US"PRIVKEY"; + case PDKIM_ERR_RSA_SIGNING: return US"SIGNING"; + case PDKIM_ERR_LONG_LINE: return US"LONG_LINE"; + case PDKIM_ERR_BUFFER_TOO_SMALL: return US"BUFFER_TOO_SMALL"; + case PDKIM_ERR_EXCESS_SIGS: return US"EXCESS_SIGS"; + case PDKIM_SIGN_PRIVKEY_WRAP: return US"PRIVKEY_WRAP"; + case PDKIM_SIGN_PRIVKEY_B64D: return US"PRIVKEY_B64D"; + default: return US"(unknown)"; + } +} + + +/* -------------------------------------------------------------------------- */ +/* Print debugging functions */ +void +pdkim_quoteprint(const uschar *data, int len) +{ +int i; +for (i = 0; i < len; i++) + { + const int c = data[i]; + switch (c) + { + case ' ' : debug_printf("{SP}"); break; + case '\t': debug_printf("{TB}"); break; + case '\r': debug_printf("{CR}"); break; + case '\n': debug_printf("{LF}"); break; + case '{' : debug_printf("{BO}"); break; + case '}' : debug_printf("{BC}"); break; + default: + if ( (c < 32) || (c > 127) ) + debug_printf("{%02x}", c); + else + debug_printf("%c", c); + break; + } + } +debug_printf("\n"); +} + +void +pdkim_hexprint(const uschar *data, int len) +{ +int i; +if (data) for (i = 0 ; i < len; i++) debug_printf("%02x", data[i]); +else debug_printf("<NULL>"); +debug_printf("\n"); +} + + + +static pdkim_stringlist * +pdkim_prepend_stringlist(pdkim_stringlist * base, const uschar * str) +{ +pdkim_stringlist * new_entry = store_get(sizeof(pdkim_stringlist)); + +memset(new_entry, 0, sizeof(pdkim_stringlist)); +new_entry->value = string_copy(str); +if (base) new_entry->next = base; +return new_entry; +} + + + +/* Trim whitespace fore & aft */ + +static void +pdkim_strtrim(gstring * str) +{ +uschar * p = str->s; +uschar * q; + +while (*p == '\t' || *p == ' ') /* dump the leading whitespace */ + { str->size--; str->ptr--; str->s++; } + +while ( str->ptr > 0 + && ((q = str->s + str->ptr - 1), (*q == '\t' || *q == ' ')) + ) + str->ptr--; /* dump trailing whitespace */ + +(void) string_from_gstring(str); +} + + + +/* -------------------------------------------------------------------------- */ + +DLLEXPORT void +pdkim_free_ctx(pdkim_ctx *ctx) +{ +} + + +/* -------------------------------------------------------------------------- */ +/* Matches the name of the passed raw "header" against + the passed colon-separated "tick", and invalidates + the entry in tick. Entries can be prefixed for multi- or over-signing, + in which case do not invalidate. + + Returns OK for a match, or fail-code +*/ + +static int +header_name_match(const uschar * header, uschar * tick) +{ +const uschar * ticklist = tick; +int sep = ':'; +BOOL multisign; +uschar * hname, * p, * ele; +uschar * hcolon = Ustrchr(header, ':'); /* Get header name */ + +if (!hcolon) + return PDKIM_FAIL; /* This isn't a header */ + +/* if we had strncmpic() we wouldn't need this copy */ +hname = string_copyn(header, hcolon-header); + +while (p = US ticklist, ele = string_nextinlist(&ticklist, &sep, NULL, 0)) + { + switch (*ele) + { + case '=': case '+': multisign = TRUE; ele++; break; + default: multisign = FALSE; break; + } + + if (strcmpic(ele, hname) == 0) + { + if (!multisign) + *p = '_'; /* Invalidate this header name instance in tick-off list */ + return PDKIM_OK; + } + } +return PDKIM_FAIL; +} + + +/* -------------------------------------------------------------------------- */ +/* Performs "relaxed" canonicalization of a header. */ + +uschar * +pdkim_relax_header_n(const uschar * header, int len, BOOL append_crlf) +{ +BOOL past_field_name = FALSE; +BOOL seen_wsp = FALSE; +const uschar * p; +uschar * relaxed = store_get(len+3); +uschar * q = relaxed; + +for (p = header; p - header < len; p++) + { + uschar c = *p; + + if (c == '\r' || c == '\n') /* Ignore CR & LF */ + continue; + if (c == '\t' || c == ' ') + { + if (seen_wsp) + continue; + c = ' '; /* Turns WSP into SP */ + seen_wsp = TRUE; + } + else + if (!past_field_name && c == ':') + { + if (seen_wsp) q--; /* This removes WSP immediately before the colon */ + seen_wsp = TRUE; /* This removes WSP immediately after the colon */ + past_field_name = TRUE; + } + else + seen_wsp = FALSE; + + /* Lowercase header name */ + if (!past_field_name) c = tolower(c); + *q++ = c; + } + +if (q > relaxed && q[-1] == ' ') q--; /* Squash eventual trailing SP */ + +if (append_crlf) { *q++ = '\r'; *q++ = '\n'; } +*q = '\0'; +return relaxed; +} + + +uschar * +pdkim_relax_header(const uschar * header, BOOL append_crlf) +{ +return pdkim_relax_header_n(header, Ustrlen(header), append_crlf); +} + + +/* -------------------------------------------------------------------------- */ +#define PDKIM_QP_ERROR_DECODE -1 + +static const uschar * +pdkim_decode_qp_char(const uschar *qp_p, int *c) +{ +const uschar *initial_pos = qp_p; + +/* Advance one char */ +qp_p++; + +/* Check for two hex digits and decode them */ +if (isxdigit(*qp_p) && isxdigit(qp_p[1])) + { + /* Do hex conversion */ + *c = (isdigit(*qp_p) ? *qp_p - '0' : toupper(*qp_p) - 'A' + 10) << 4; + *c |= isdigit(qp_p[1]) ? qp_p[1] - '0' : toupper(qp_p[1]) - 'A' + 10; + return qp_p + 2; + } + +/* Illegal char here */ +*c = PDKIM_QP_ERROR_DECODE; +return initial_pos; +} + + +/* -------------------------------------------------------------------------- */ + +static uschar * +pdkim_decode_qp(const uschar * str) +{ +int nchar = 0; +uschar * q; +const uschar * p = str; +uschar * n = store_get(Ustrlen(str)+1); + +*n = '\0'; +q = n; +while (*p) + { + if (*p == '=') + { + p = pdkim_decode_qp_char(p, &nchar); + if (nchar >= 0) + { + *q++ = nchar; + continue; + } + } + else + *q++ = *p; + p++; + } +*q = '\0'; +return n; +} + + +/* -------------------------------------------------------------------------- */ + +void +pdkim_decode_base64(const uschar * str, blob * b) +{ +int dlen = b64decode(str, &b->data); +if (dlen < 0) b->data = NULL; +b->len = dlen; +} + +uschar * +pdkim_encode_base64(blob * b) +{ +return b64encode(b->data, b->len); +} + + +/* -------------------------------------------------------------------------- */ +#define PDKIM_HDR_LIMBO 0 +#define PDKIM_HDR_TAG 1 +#define PDKIM_HDR_VALUE 2 + +static pdkim_signature * +pdkim_parse_sig_header(pdkim_ctx * ctx, uschar * raw_hdr) +{ +pdkim_signature * sig; +uschar *p, *q; +gstring * cur_tag = NULL; +gstring * cur_val = NULL; +BOOL past_hname = FALSE; +BOOL in_b_val = FALSE; +int where = PDKIM_HDR_LIMBO; +int i; + +sig = store_get(sizeof(pdkim_signature)); +memset(sig, 0, sizeof(pdkim_signature)); +sig->bodylength = -1; + +/* Set so invalid/missing data error display is accurate */ +sig->version = 0; +sig->keytype = -1; +sig->hashtype = -1; + +q = sig->rawsig_no_b_val = store_get(Ustrlen(raw_hdr)+1); + +for (p = raw_hdr; ; p++) + { + char c = *p; + + /* Ignore FWS */ + if (c == '\r' || c == '\n') + goto NEXT_CHAR; + + /* Fast-forward through header name */ + if (!past_hname) + { + if (c == ':') past_hname = TRUE; + goto NEXT_CHAR; + } + + if (where == PDKIM_HDR_LIMBO) + { + /* In limbo, just wait for a tag-char to appear */ + if (!(c >= 'a' && c <= 'z')) + goto NEXT_CHAR; + + where = PDKIM_HDR_TAG; + } + + if (where == PDKIM_HDR_TAG) + { + if (c >= 'a' && c <= 'z') + cur_tag = string_catn(cur_tag, p, 1); + + if (c == '=') + { + if (Ustrcmp(string_from_gstring(cur_tag), "b") == 0) + { + *q++ = '='; + in_b_val = TRUE; + } + where = PDKIM_HDR_VALUE; + goto NEXT_CHAR; + } + } + + if (where == PDKIM_HDR_VALUE) + { + if (c == '\r' || c == '\n' || c == ' ' || c == '\t') + goto NEXT_CHAR; + + if (c == ';' || c == '\0') + { + /* We must have both tag and value, and tags must be one char except + for the possibility of "bh". */ + + if ( cur_tag && cur_val + && (cur_tag->ptr == 1 || *cur_tag->s == 'b') + ) + { + (void) string_from_gstring(cur_val); + pdkim_strtrim(cur_val); + + DEBUG(D_acl) debug_printf(" %s=%s\n", cur_tag->s, cur_val->s); + + switch (*cur_tag->s) + { + case 'b': /* sig-data or body-hash */ + switch (cur_tag->s[1]) + { + case '\0': pdkim_decode_base64(cur_val->s, &sig->sighash); break; + case 'h': if (cur_tag->ptr == 2) + pdkim_decode_base64(cur_val->s, &sig->bodyhash); + break; + default: break; + } + break; + case 'v': /* version */ + /* We only support version 1, and that is currently the + only version there is. */ + sig->version = + Ustrcmp(cur_val->s, PDKIM_SIGNATURE_VERSION) == 0 ? 1 : -1; + break; + case 'a': /* algorithm */ + { + const uschar * list = cur_val->s; + int sep = '-'; + uschar * elem; + + if ((elem = string_nextinlist(&list, &sep, NULL, 0))) + for(i = 0; i < nelem(pdkim_keytypes); i++) + if (Ustrcmp(elem, pdkim_keytypes[i]) == 0) + { sig->keytype = i; break; } + if ((elem = string_nextinlist(&list, &sep, NULL, 0))) + for (i = 0; i < nelem(pdkim_hashes); i++) + if (Ustrcmp(elem, pdkim_hashes[i].dkim_hashname) == 0) + { sig->hashtype = i; break; } + } + + case 'c': /* canonicalization */ + pdkim_cstring_to_canons(cur_val->s, 0, + &sig->canon_headers, &sig->canon_body); + break; + case 'q': /* Query method (for pubkey)*/ + for (i = 0; pdkim_querymethods[i]; i++) + if (Ustrcmp(cur_val->s, pdkim_querymethods[i]) == 0) + { + sig->querymethod = i; /* we never actually use this */ + break; + } + break; + case 's': /* Selector */ + sig->selector = string_copyn(cur_val->s, cur_val->ptr); break; + case 'd': /* SDID */ + sig->domain = string_copyn(cur_val->s, cur_val->ptr); break; + case 'i': /* AUID */ + sig->identity = pdkim_decode_qp(cur_val->s); break; + case 't': /* Timestamp */ + sig->created = strtoul(CS cur_val->s, NULL, 10); break; + case 'x': /* Expiration */ + sig->expires = strtoul(CS cur_val->s, NULL, 10); break; + case 'l': /* Body length count */ + sig->bodylength = strtol(CS cur_val->s, NULL, 10); break; + case 'h': /* signed header fields */ + sig->headernames = string_copyn(cur_val->s, cur_val->ptr); break; + case 'z': /* Copied headfields */ + sig->copiedheaders = pdkim_decode_qp(cur_val->s); break; +/*XXX draft-ietf-dcrup-dkim-crypto-05 would need 'p' tag support +for rsafp signatures. But later discussion is dropping those. */ + default: + DEBUG(D_acl) debug_printf(" Unknown tag encountered\n"); + break; + } + } + cur_tag = cur_val = NULL; + in_b_val = FALSE; + where = PDKIM_HDR_LIMBO; + } + else + cur_val = string_catn(cur_val, p, 1); + } + +NEXT_CHAR: + if (c == '\0') + break; + + if (!in_b_val) + *q++ = c; + } + +if (sig->keytype < 0 || sig->hashtype < 0) /* Cannot verify this signature */ + return NULL; + +*q = '\0'; +/* Chomp raw header. The final newline must not be added to the signature. */ +while (--q > sig->rawsig_no_b_val && (*q == '\r' || *q == '\n')) + *q = '\0'; + +DEBUG(D_acl) + { + debug_printf( + "PDKIM >> Raw signature w/o b= tag value >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n"); + pdkim_quoteprint(US sig->rawsig_no_b_val, Ustrlen(sig->rawsig_no_b_val)); + debug_printf( + "PDKIM >> Sig size: %4u bits\n", (unsigned) sig->sighash.len*8); + debug_printf( + "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + } + +if (!pdkim_set_sig_bodyhash(ctx, sig)) + return NULL; + +return sig; +} + + +/* -------------------------------------------------------------------------- */ + +pdkim_pubkey * +pdkim_parse_pubkey_record(const uschar *raw_record) +{ +const uschar * ele; +int sep = ';'; +pdkim_pubkey * pub; + +pub = store_get(sizeof(pdkim_pubkey)); +memset(pub, 0, sizeof(pdkim_pubkey)); + +while ((ele = string_nextinlist(&raw_record, &sep, NULL, 0))) + { + const uschar * val; + + if ((val = Ustrchr(ele, '='))) + { + int taglen = val++ - ele; + + DEBUG(D_acl) debug_printf(" %.*s=%s\n", taglen, ele, val); + switch (ele[0]) + { + case 'v': pub->version = val; break; + case 'h': pub->hashes = val; break; + case 'k': pub->keytype = val; break; + case 'g': pub->granularity = val; break; + case 'n': pub->notes = pdkim_decode_qp(val); break; + case 'p': pdkim_decode_base64(val, &pub->key); break; + case 's': pub->srvtype = val; break; + case 't': if (Ustrchr(val, 'y')) pub->testing = 1; + if (Ustrchr(val, 's')) pub->no_subdomaining = 1; + break; + default: DEBUG(D_acl) debug_printf(" Unknown tag encountered\n"); break; + } + } + } + +/* Set fallback defaults */ +if (!pub->version) + pub->version = string_copy(PDKIM_PUB_RECORD_VERSION); +else if (Ustrcmp(pub->version, PDKIM_PUB_RECORD_VERSION) != 0) + { + DEBUG(D_acl) debug_printf(" Bad v= field\n"); + return NULL; + } + +if (!pub->granularity) pub->granularity = US"*"; +if (!pub->keytype ) pub->keytype = US"rsa"; +if (!pub->srvtype ) pub->srvtype = US"*"; + +/* p= is required */ +if (pub->key.data) + return pub; + +DEBUG(D_acl) debug_printf(" Missing p= field\n"); +return NULL; +} + + +/* -------------------------------------------------------------------------- */ + +/* Update one bodyhash with some additional data. +If we have to relax the data for this sig, return our copy of it. */ + +static blob * +pdkim_update_ctx_bodyhash(pdkim_bodyhash * b, blob * orig_data, blob * relaxed_data) +{ +blob * canon_data = orig_data; +/* Defaults to simple canon (no further treatment necessary) */ + +if (b->canon_method == PDKIM_CANON_RELAXED) + { + /* Relax the line if not done already */ + if (!relaxed_data) + { + BOOL seen_wsp = FALSE; + const uschar * p, * r; + int q = 0; + + /* We want to be able to free this else we allocate + for the entire message which could be many MB. Since + we don't know what allocations the SHA routines might + do, not safe to use store_get()/store_reset(). */ + + relaxed_data = store_malloc(sizeof(blob) + orig_data->len+1); + relaxed_data->data = US (relaxed_data+1); + + for (p = orig_data->data, r = p + orig_data->len; p < r; p++) + { + char c = *p; + if (c == '\r') + { + if (q > 0 && relaxed_data->data[q-1] == ' ') + q--; + } + else if (c == '\t' || c == ' ') + { + c = ' '; /* Turns WSP into SP */ + if (seen_wsp) + continue; + seen_wsp = TRUE; + } + else + seen_wsp = FALSE; + relaxed_data->data[q++] = c; + } + relaxed_data->data[q] = '\0'; + relaxed_data->len = q; + } + canon_data = relaxed_data; + } + +/* Make sure we don't exceed the to-be-signed body length */ +if ( b->bodylength >= 0 + && b->signed_body_bytes + (unsigned long)canon_data->len > b->bodylength + ) + canon_data->len = b->bodylength - b->signed_body_bytes; + +if (canon_data->len > 0) + { + exim_sha_update(&b->body_hash_ctx, CUS canon_data->data, canon_data->len); + b->signed_body_bytes += canon_data->len; + DEBUG(D_acl) pdkim_quoteprint(canon_data->data, canon_data->len); + } + +return relaxed_data; +} + + +/* -------------------------------------------------------------------------- */ + +static void +pdkim_finish_bodyhash(pdkim_ctx * ctx) +{ +pdkim_bodyhash * b; +pdkim_signature * sig; + +for (b = ctx->bodyhash; b; b = b->next) /* Finish hashes */ + { + DEBUG(D_acl) debug_printf("PDKIM: finish bodyhash %d/%d/%ld len %ld\n", + b->hashtype, b->canon_method, b->bodylength, b->signed_body_bytes); + exim_sha_finish(&b->body_hash_ctx, &b->bh); + } + +/* Traverse all signatures */ +for (sig = ctx->sig; sig; sig = sig->next) + { + b = sig->calc_body_hash; + + DEBUG(D_acl) + { + debug_printf("PDKIM [%s] Body bytes (%s) hashed: %lu\n" + "PDKIM [%s] Body %s computed: ", + sig->domain, pdkim_canons[b->canon_method], b->signed_body_bytes, + sig->domain, pdkim_hashes[b->hashtype].dkim_hashname); + pdkim_hexprint(CUS b->bh.data, b->bh.len); + } + + /* SIGNING -------------------------------------------------------------- */ + if (ctx->flags & PDKIM_MODE_SIGN) + { + /* If bodylength limit is set, and we have received less bytes + than the requested amount, effectively remove the limit tag. */ + if (b->signed_body_bytes < sig->bodylength) + sig->bodylength = -1; + } + + else + /* VERIFICATION --------------------------------------------------------- */ + /* Be careful that the header sig included a bodyash */ + + if ( sig->bodyhash.data + && memcmp(b->bh.data, sig->bodyhash.data, b->bh.len) == 0) + { + DEBUG(D_acl) debug_printf("PDKIM [%s] Body hash compared OK\n", sig->domain); + } + else + { + DEBUG(D_acl) + { + debug_printf("PDKIM [%s] Body hash signature from headers: ", sig->domain); + pdkim_hexprint(sig->bodyhash.data, sig->bodyhash.len); + debug_printf("PDKIM [%s] Body hash did NOT verify\n", sig->domain); + } + sig->verify_status = PDKIM_VERIFY_FAIL; + sig->verify_ext_status = PDKIM_VERIFY_FAIL_BODY; + } + } +} + + + +static void +pdkim_body_complete(pdkim_ctx * ctx) +{ +pdkim_bodyhash * b; + +/* In simple body mode, if any empty lines were buffered, +replace with one. rfc 4871 3.4.3 */ +/*XXX checking the signed-body-bytes is a gross hack; I think +it indicates that all linebreaks should be buffered, including +the one terminating a text line */ + +for (b = ctx->bodyhash; b; b = b->next) + if ( b->canon_method == PDKIM_CANON_SIMPLE + && b->signed_body_bytes == 0 + && b->num_buffered_blanklines > 0 + ) + (void) pdkim_update_ctx_bodyhash(b, &lineending, NULL); + +ctx->flags |= PDKIM_SEEN_EOD; +ctx->linebuf_offset = 0; +} + + + +/* -------------------------------------------------------------------------- */ +/* Call from pdkim_feed below for processing complete body lines */ +/* NOTE: the line is not NUL-terminated; but we have a count */ + +static void +pdkim_bodyline_complete(pdkim_ctx * ctx) +{ +blob line = {.data = ctx->linebuf, .len = ctx->linebuf_offset}; +pdkim_bodyhash * b; +blob * rnl = NULL; +blob * rline = NULL; + +/* Ignore extra data if we've seen the end-of-data marker */ +if (ctx->flags & PDKIM_SEEN_EOD) goto all_skip; + +/* We've always got one extra byte to stuff a zero ... */ +ctx->linebuf[line.len] = '\0'; + +/* Terminate on EOD marker */ +if (ctx->flags & PDKIM_DOT_TERM) + { + if (memcmp(line.data, ".\r\n", 3) == 0) + { pdkim_body_complete(ctx); return; } + + /* Unstuff dots */ + if (memcmp(line.data, "..", 2) == 0) + { line.data++; line.len--; } + } + +/* Empty lines need to be buffered until we find a non-empty line */ +if (memcmp(line.data, "\r\n", 2) == 0) + { + for (b = ctx->bodyhash; b; b = b->next) b->num_buffered_blanklines++; + goto all_skip; + } + +/* Process line for each bodyhash separately */ +for (b = ctx->bodyhash; b; b = b->next) + { + if (b->canon_method == PDKIM_CANON_RELAXED) + { + /* Lines with just spaces need to be buffered too */ + uschar * cp = line.data; + char c; + + while ((c = *cp)) + { + if (c == '\r' && cp[1] == '\n') break; + if (c != ' ' && c != '\t') goto hash_process; + cp++; + } + + b->num_buffered_blanklines++; + goto hash_skip; + } + +hash_process: + /* At this point, we have a non-empty line, so release the buffered ones. */ + + while (b->num_buffered_blanklines) + { + rnl = pdkim_update_ctx_bodyhash(b, &lineending, rnl); + b->num_buffered_blanklines--; + } + + rline = pdkim_update_ctx_bodyhash(b, &line, rline); +hash_skip: ; + } + +if (rnl) store_free(rnl); +if (rline) store_free(rline); + +all_skip: + +ctx->linebuf_offset = 0; +return; +} + + +/* -------------------------------------------------------------------------- */ +/* Callback from pdkim_feed below for processing complete headers */ +#define DKIM_SIGNATURE_HEADERNAME "DKIM-Signature:" + +static int +pdkim_header_complete(pdkim_ctx * ctx) +{ +pdkim_signature * sig, * last_sig; + +/* Special case: The last header can have an extra \r appended */ +if ( (ctx->cur_header->ptr > 1) && + (ctx->cur_header->s[ctx->cur_header->ptr-1] == '\r') ) + --ctx->cur_header->ptr; +(void) string_from_gstring(ctx->cur_header); + +#ifdef EXPERIMENTAL_ARC +/* Feed the header line to ARC processing */ +(void) arc_header_feed(ctx->cur_header, !(ctx->flags & PDKIM_MODE_SIGN)); +#endif + +if (++ctx->num_headers > PDKIM_MAX_HEADERS) goto BAIL; + +/* SIGNING -------------------------------------------------------------- */ +if (ctx->flags & PDKIM_MODE_SIGN) + for (sig = ctx->sig; sig; sig = sig->next) /* Traverse all signatures */ + + /* Add header to the signed headers list (in reverse order) */ + sig->headers = pdkim_prepend_stringlist(sig->headers, ctx->cur_header->s); + +/* VERIFICATION ----------------------------------------------------------- */ +/* DKIM-Signature: headers are added to the verification list */ +else + { +#ifdef notdef + DEBUG(D_acl) + { + debug_printf("PDKIM >> raw hdr: "); + pdkim_quoteprint(CUS ctx->cur_header->s, ctx->cur_header->ptr); + } +#endif + if (strncasecmp(CCS ctx->cur_header->s, + DKIM_SIGNATURE_HEADERNAME, + Ustrlen(DKIM_SIGNATURE_HEADERNAME)) == 0) + { + /* Create and chain new signature block. We could error-check for all + required tags here, but prefer to create the internal sig and expicitly + fail verification of it later. */ + + DEBUG(D_acl) debug_printf( + "PDKIM >> Found sig, trying to parse >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n"); + + sig = pdkim_parse_sig_header(ctx, ctx->cur_header->s); + + if (!(last_sig = ctx->sig)) + ctx->sig = sig; + else + { + while (last_sig->next) last_sig = last_sig->next; + last_sig->next = sig; + } + + if (--dkim_collect_input == 0) + { + ctx->headers = pdkim_prepend_stringlist(ctx->headers, ctx->cur_header->s); + ctx->cur_header->s[ctx->cur_header->ptr = 0] = '\0'; + return PDKIM_ERR_EXCESS_SIGS; + } + } + + /* all headers are stored for signature verification */ + ctx->headers = pdkim_prepend_stringlist(ctx->headers, ctx->cur_header->s); + } + +BAIL: +ctx->cur_header->s[ctx->cur_header->ptr = 0] = '\0'; /* leave buffer for reuse */ +return PDKIM_OK; +} + + + +/* -------------------------------------------------------------------------- */ +#define HEADER_BUFFER_FRAG_SIZE 256 + +DLLEXPORT int +pdkim_feed(pdkim_ctx * ctx, uschar * data, int len) +{ +int p, rc; + +/* Alternate EOD signal, used in non-dotstuffing mode */ +if (!data) + pdkim_body_complete(ctx); + +else for (p = 0; p < len; p++) + { + uschar c = data[p]; + + if (ctx->flags & PDKIM_PAST_HDRS) + { + if (c == '\n' && !(ctx->flags & PDKIM_SEEN_CR)) /* emulate the CR */ + { + ctx->linebuf[ctx->linebuf_offset++] = '\r'; + if (ctx->linebuf_offset == PDKIM_MAX_BODY_LINE_LEN-1) + return PDKIM_ERR_LONG_LINE; + } + + /* Processing body byte */ + ctx->linebuf[ctx->linebuf_offset++] = c; + if (c == '\r') + ctx->flags |= PDKIM_SEEN_CR; + else if (c == '\n') + { + ctx->flags &= ~PDKIM_SEEN_CR; + pdkim_bodyline_complete(ctx); + } + + if (ctx->linebuf_offset == PDKIM_MAX_BODY_LINE_LEN-1) + return PDKIM_ERR_LONG_LINE; + } + else + { + /* Processing header byte */ + if (c == '\r') + ctx->flags |= PDKIM_SEEN_CR; + else if (c == '\n') + { + if (!(ctx->flags & PDKIM_SEEN_CR)) /* emulate the CR */ + ctx->cur_header = string_catn(ctx->cur_header, CUS "\r", 1); + + if (ctx->flags & PDKIM_SEEN_LF) /* Seen last header line */ + { + if ((rc = pdkim_header_complete(ctx)) != PDKIM_OK) + return rc; + + ctx->flags = (ctx->flags & ~(PDKIM_SEEN_LF|PDKIM_SEEN_CR)) | PDKIM_PAST_HDRS; + DEBUG(D_acl) debug_printf( + "PDKIM >> Body data for hash, canonicalized >>>>>>>>>>>>>>>>>>>>>>>>>>>>\n"); + continue; + } + else + ctx->flags = (ctx->flags & ~PDKIM_SEEN_CR) | PDKIM_SEEN_LF; + } + else if (ctx->flags & PDKIM_SEEN_LF) + { + if (!(c == '\t' || c == ' ')) /* End of header */ + if ((rc = pdkim_header_complete(ctx)) != PDKIM_OK) + return rc; + ctx->flags &= ~PDKIM_SEEN_LF; + } + + if (!ctx->cur_header || ctx->cur_header->ptr < PDKIM_MAX_HEADER_LEN) + ctx->cur_header = string_catn(ctx->cur_header, CUS &data[p], 1); + } + } +return PDKIM_OK; +} + + + +/* Extend a growing header with a continuation-linebreak */ +static gstring * +pdkim_hdr_cont(gstring * str, int * col) +{ +*col = 1; +return string_catn(str, US"\r\n\t", 3); +} + + + +/* + * RFC 5322 specifies that header line length SHOULD be no more than 78 + * lets make it so! + * pdkim_headcat + * + * returns uschar * (not nul-terminated) + * + * col: this int holds and receives column number (octets since last '\n') + * str: partial string to append to + * pad: padding, split line or space after before or after eg: ";" + * intro: - must join to payload eg "h=", usually the tag name + * payload: eg base64 data - long data can be split arbitrarily. + * + * this code doesn't fold the header in some of the places that RFC4871 + * allows: As per RFC5322(2.2.3) it only folds before or after tag-value + * pairs and inside long values. it also always spaces or breaks after the + * "pad" + * + * no guarantees are made for output given out-of range input. like tag + * names longer than 78, or bogus col. Input is assumed to be free of line breaks. + */ + +static gstring * +pdkim_headcat(int * col, gstring * str, + const uschar * pad, const uschar * intro, const uschar * payload) +{ +size_t l; + +if (pad) + { + l = Ustrlen(pad); + if (*col + l > 78) + str = pdkim_hdr_cont(str, col); + str = string_catn(str, pad, l); + *col += l; + } + +l = (pad?1:0) + (intro?Ustrlen(intro):0); + +if (*col + l > 78) + { /*can't fit intro - start a new line to make room.*/ + str = pdkim_hdr_cont(str, col); + l = intro?Ustrlen(intro):0; + } + +l += payload ? Ustrlen(payload):0 ; + +while (l>77) + { /* this fragment will not fit on a single line */ + if (pad) + { + str = string_catn(str, US" ", 1); + *col += 1; + pad = NULL; /* only want this once */ + l--; + } + + if (intro) + { + size_t sl = Ustrlen(intro); + + str = string_catn(str, intro, sl); + *col += sl; + l -= sl; + intro = NULL; /* only want this once */ + } + + if (payload) + { + size_t sl = Ustrlen(payload); + size_t chomp = *col+sl < 77 ? sl : 78-*col; + + str = string_catn(str, payload, chomp); + *col += chomp; + payload += chomp; + l -= chomp-1; + } + + /* the while precondition tells us it didn't fit. */ + str = pdkim_hdr_cont(str, col); + } + +if (*col + l > 78) + { + str = pdkim_hdr_cont(str, col); + pad = NULL; + } + +if (pad) + { + str = string_catn(str, US" ", 1); + *col += 1; + pad = NULL; + } + +if (intro) + { + size_t sl = Ustrlen(intro); + + str = string_catn(str, intro, sl); + *col += sl; + l -= sl; + intro = NULL; + } + +if (payload) + { + size_t sl = Ustrlen(payload); + + str = string_catn(str, payload, sl); + *col += sl; + } + +return str; +} + + +/* -------------------------------------------------------------------------- */ + +/* Signing: create signature header +*/ +static uschar * +pdkim_create_header(pdkim_signature * sig, BOOL final) +{ +uschar * base64_bh; +uschar * base64_b; +int col = 0; +gstring * hdr; +gstring * canon_all; + +canon_all = string_cat (NULL, pdkim_canons[sig->canon_headers]); +canon_all = string_catn(canon_all, US"/", 1); +canon_all = string_cat (canon_all, pdkim_canons[sig->canon_body]); +(void) string_from_gstring(canon_all); + +hdr = string_cat(NULL, US"DKIM-Signature: v="PDKIM_SIGNATURE_VERSION); +col = hdr->ptr; + +/* Required and static bits */ +hdr = pdkim_headcat(&col, hdr, US";", US"a=", dkim_sig_to_a_tag(sig)); +hdr = pdkim_headcat(&col, hdr, US";", US"q=", pdkim_querymethods[sig->querymethod]); +hdr = pdkim_headcat(&col, hdr, US";", US"c=", canon_all->s); +hdr = pdkim_headcat(&col, hdr, US";", US"d=", sig->domain); +hdr = pdkim_headcat(&col, hdr, US";", US"s=", sig->selector); + +/* list of header names can be split between items. */ + { + uschar * n = string_copy(sig->headernames); + uschar * i = US"h="; + uschar * s = US";"; + + while (*n) + { + uschar * c = Ustrchr(n, ':'); + + if (c) *c ='\0'; + + if (!i) + hdr = pdkim_headcat(&col, hdr, NULL, NULL, US":"); + + hdr = pdkim_headcat(&col, hdr, s, i, n); + + if (!c) + break; + + n = c+1; + s = NULL; + i = NULL; + } + } + +base64_bh = pdkim_encode_base64(&sig->calc_body_hash->bh); +hdr = pdkim_headcat(&col, hdr, US";", US"bh=", base64_bh); + +/* Optional bits */ +if (sig->identity) + hdr = pdkim_headcat(&col, hdr, US";", US"i=", sig->identity); + +if (sig->created > 0) + { + uschar minibuf[20]; + + snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->created); + hdr = pdkim_headcat(&col, hdr, US";", US"t=", minibuf); +} + +if (sig->expires > 0) + { + uschar minibuf[20]; + + snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->expires); + hdr = pdkim_headcat(&col, hdr, US";", US"x=", minibuf); + } + +if (sig->bodylength >= 0) + { + uschar minibuf[20]; + + snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->bodylength); + hdr = pdkim_headcat(&col, hdr, US";", US"l=", minibuf); + } + +/* Preliminary or final version? */ +if (final) + { + base64_b = pdkim_encode_base64(&sig->sighash); + hdr = pdkim_headcat(&col, hdr, US";", US"b=", base64_b); + + /* add trailing semicolon: I'm not sure if this is actually needed */ + hdr = pdkim_headcat(&col, hdr, NULL, US";", US""); + } +else + { + /* To satisfy the rule "all surrounding whitespace [...] deleted" + ( RFC 6376 section 3.7 ) we ensure there is no whitespace here. Otherwise + the headcat routine could insert a linebreak which the relaxer would reduce + to a single space preceding the terminating semicolon, resulting in an + incorrect header-hash. */ + hdr = pdkim_headcat(&col, hdr, US";", US"b=;", US""); + } + +return string_from_gstring(hdr); +} + + +/* -------------------------------------------------------------------------- */ + +/* According to draft-ietf-dcrup-dkim-crypto-07 "keys are 256 bits" (referring +to DNS, hence the pubkey). Check for more than 32 bytes; if so assume the +alternate possible representation (still) being discussed: a +SubjectPublickeyInfo wrapped key - and drop all but the trailing 32-bytes (it +should be a DER, with exactly 12 leading bytes - but we could accept a BER also, +which could be any size). We still rely on the crypto library for checking for +undersize. + +When the RFC is published this should be re-addressed. */ + +static void +check_bare_ed25519_pubkey(pdkim_pubkey * p) +{ +int excess = p->key.len - 32; +if (excess > 0) + { + DEBUG(D_acl) debug_printf("PDKIM: unexpected pubkey len %lu\n", p->key.len); + p->key.data += excess; p->key.len = 32; + } +} + + +static pdkim_pubkey * +pdkim_key_from_dns(pdkim_ctx * ctx, pdkim_signature * sig, ev_ctx * vctx, + const uschar ** errstr) +{ +uschar * dns_txt_name, * dns_txt_reply; +pdkim_pubkey * p; + +/* Fetch public key for signing domain, from DNS */ + +dns_txt_name = string_sprintf("%s._domainkey.%s.", sig->selector, sig->domain); + +if ( !(dns_txt_reply = ctx->dns_txt_callback(dns_txt_name)) + || dns_txt_reply[0] == '\0' + ) + { + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE; + return NULL; + } + +DEBUG(D_acl) + { + debug_printf( + "PDKIM >> Parsing public key record >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n" + " %s\n" + " Raw record: ", + dns_txt_name); + pdkim_quoteprint(CUS dns_txt_reply, Ustrlen(dns_txt_reply)); + } + +if ( !(p = pdkim_parse_pubkey_record(CUS dns_txt_reply)) + || (Ustrcmp(p->srvtype, "*") != 0 && Ustrcmp(p->srvtype, "email") != 0) + ) + { + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD; + + DEBUG(D_acl) + { + if (p) + debug_printf(" Invalid public key service type '%s'\n", p->srvtype); + else + debug_printf(" Error while parsing public key record\n"); + debug_printf( + "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + } + return NULL; + } + +DEBUG(D_acl) debug_printf( + "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + +/* Import public key */ + +/* Normally we use the signature a= tag to tell us the pubkey format. +When signing under debug we do a test-import of the pubkey, and at that +time we do not have a signature so we must interpret the pubkey k= tag +instead. Assume writing on the sig is ok in that case. */ + +if (sig->keytype < 0) + { + int i; + for(i = 0; i < nelem(pdkim_keytypes); i++) + if (Ustrcmp(p->keytype, pdkim_keytypes[i]) == 0) + { sig->keytype = i; goto k_ok; } + DEBUG(D_acl) debug_printf("verify_init: unhandled keytype %s\n", p->keytype); + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_IMPORT; + return NULL; + } +k_ok: + +if (sig->keytype == KEYTYPE_ED25519) + check_bare_ed25519_pubkey(p); + +if ((*errstr = exim_dkim_verify_init(&p->key, + sig->keytype == KEYTYPE_ED25519 ? KEYFMT_ED25519_BARE : KEYFMT_DER, + vctx))) + { + DEBUG(D_acl) debug_printf("verify_init: %s\n", *errstr); + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_IMPORT; + return NULL; + } + +vctx->keytype = sig->keytype; +return p; +} + + +/* -------------------------------------------------------------------------- */ + +DLLEXPORT int +pdkim_feed_finish(pdkim_ctx * ctx, pdkim_signature ** return_signatures, + const uschar ** err) +{ +pdkim_bodyhash * b; +pdkim_signature * sig; +BOOL verify_pass = FALSE; + +/* Check if we must still flush a (partial) header. If that is the + case, the message has no body, and we must compute a body hash + out of '<CR><LF>' */ +if (ctx->cur_header && ctx->cur_header->ptr > 0) + { + blob * rnl = NULL; + int rc; + + if ((rc = pdkim_header_complete(ctx)) != PDKIM_OK) + return rc; + + for (b = ctx->bodyhash; b; b = b->next) + rnl = pdkim_update_ctx_bodyhash(b, &lineending, rnl); + if (rnl) store_free(rnl); + } +else + DEBUG(D_acl) debug_printf( + "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + +/* Build (and/or evaluate) body hash. Do this even if no DKIM sigs, in case we +have a hash to do for ARC. */ + +pdkim_finish_bodyhash(ctx); + +if (!ctx->sig) + { + DEBUG(D_acl) debug_printf("PDKIM: no signatures\n"); + *return_signatures = NULL; + return PDKIM_OK; + } + +for (sig = ctx->sig; sig; sig = sig->next) + { + hctx hhash_ctx; + uschar * sig_hdr = US""; + blob hhash; + gstring * hdata = NULL; + es_ctx sctx; + + if ( !(ctx->flags & PDKIM_MODE_SIGN) + && sig->verify_status == PDKIM_VERIFY_FAIL) + { + DEBUG(D_acl) + debug_printf("PDKIM: [%s] abandoning this signature\n", sig->domain); + continue; + } + + /*XXX The hash of the headers is needed for GCrypt (for which we can do RSA + suging only, as it happens) and for either GnuTLS and OpenSSL when we are + signing with EC (specifically, Ed25519). The former is because the GCrypt + signing operation is pure (does not do its own hash) so we must hash. The + latter is because we (stupidly, but this is what the IETF draft is saying) + must hash with the declared hash method, then pass the result to the library + hash-and-sign routine (because that's all the libraries are providing. And + we're stuck with whatever that hidden hash method is, too). We may as well + do this hash incrementally. + We don't need the hash we're calculating here for the GnuTLS and OpenSSL + cases of RSA signing, since those library routines can do hash-and-sign. + + Some time in the future we could easily avoid doing the hash here for those + cases (which will be common for a long while. We could also change from + the current copy-all-the-headers-into-one-block, then call the hash-and-sign + implementation - to a proper incremental one. Unfortunately, GnuTLS just + cannot do incremental - either signing or verification. Unsure about GCrypt. + */ + + /*XXX The header hash is also used (so far) by the verify operation */ + + if (!exim_sha_init(&hhash_ctx, pdkim_hashes[sig->hashtype].exim_hashmethod)) + { + log_write(0, LOG_MAIN|LOG_PANIC, + "PDKIM: hash setup error, possibly nonhandled hashtype"); + break; + } + + if (ctx->flags & PDKIM_MODE_SIGN) + DEBUG(D_acl) debug_printf( + "PDKIM >> Headers to be signed: >>>>>>>>>>>>\n" + " %s\n", + sig->sign_headers); + + DEBUG(D_acl) debug_printf( + "PDKIM >> Header data for hash, canonicalized (%-7s), in sequence >>\n", + pdkim_canons[sig->canon_headers]); + + + /* SIGNING ---------------------------------------------------------------- */ + /* When signing, walk through our header list and add them to the hash. As we + go, construct a list of the header's names to use for the h= parameter. + Then append to that list any remaining header names for which there was no + header to sign. */ + + if (ctx->flags & PDKIM_MODE_SIGN) + { + gstring * g = NULL; + pdkim_stringlist *p; + const uschar * l; + uschar * s; + int sep = 0; + + /* Import private key, including the keytype which we need for building + the signature header */ + +/*XXX extend for non-RSA algos */ + if ((*err = exim_dkim_signing_init(CUS sig->privkey, &sctx))) + { + log_write(0, LOG_MAIN|LOG_PANIC, "signing_init: %s", *err); + return PDKIM_ERR_RSA_PRIVKEY; + } + sig->keytype = sctx.keytype; + + for (sig->headernames = NULL, /* Collected signed header names */ + p = sig->headers; p; p = p->next) + { + uschar * rh = p->value; + + if (header_name_match(rh, sig->sign_headers) == PDKIM_OK) + { + /* Collect header names (Note: colon presence is guaranteed here) */ + g = string_append_listele_n(g, ':', rh, Ustrchr(rh, ':') - rh); + + if (sig->canon_headers == PDKIM_CANON_RELAXED) + rh = pdkim_relax_header(rh, TRUE); /* cook header for relaxed canon */ + + /* Feed header to the hash algorithm */ + exim_sha_update(&hhash_ctx, CUS rh, Ustrlen(rh)); + + /* Remember headers block for signing (when the library cannot do incremental) */ + /*XXX we could avoid doing this for all but the GnuTLS/RSA case */ + hdata = exim_dkim_data_append(hdata, rh); + + DEBUG(D_acl) pdkim_quoteprint(rh, Ustrlen(rh)); + } + } + + /* Any headers we wanted to sign but were not present must also be listed. + Ignore elements that have been ticked-off or are marked as never-oversign. */ + + l = sig->sign_headers; + while((s = string_nextinlist(&l, &sep, NULL, 0))) + { + if (*s == '+') /* skip oversigning marker */ + s++; + if (*s != '_' && *s != '=') + g = string_append_listele(g, ':', s); + } + sig->headernames = string_from_gstring(g); + + /* Create signature header with b= omitted */ + sig_hdr = pdkim_create_header(sig, FALSE); + } + + /* VERIFICATION ----------------------------------------------------------- */ + /* When verifying, walk through the header name list in the h= parameter and + add the headers to the hash in that order. */ + else + { + uschar * p = sig->headernames; + uschar * q; + pdkim_stringlist * hdrs; + + if (p) + { + /* clear tags */ + for (hdrs = ctx->headers; hdrs; hdrs = hdrs->next) + hdrs->tag = 0; + + p = string_copy(p); + while(1) + { + if ((q = Ustrchr(p, ':'))) + *q = '\0'; + + /*XXX walk the list of headers in same order as received. */ + for (hdrs = ctx->headers; hdrs; hdrs = hdrs->next) + if ( hdrs->tag == 0 + && strncasecmp(CCS hdrs->value, CCS p, Ustrlen(p)) == 0 + && (hdrs->value)[Ustrlen(p)] == ':' + ) + { + /* cook header for relaxed canon, or just copy it for simple */ + + uschar * rh = sig->canon_headers == PDKIM_CANON_RELAXED + ? pdkim_relax_header(hdrs->value, TRUE) + : string_copy(CUS hdrs->value); + + /* Feed header to the hash algorithm */ + exim_sha_update(&hhash_ctx, CUS rh, Ustrlen(rh)); + + DEBUG(D_acl) pdkim_quoteprint(rh, Ustrlen(rh)); + hdrs->tag = 1; + break; + } + + if (!q) break; + p = q+1; + } + + sig_hdr = string_copy(sig->rawsig_no_b_val); + } + } + + DEBUG(D_acl) debug_printf( + "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + + DEBUG(D_acl) + { + debug_printf( + "PDKIM >> Signed DKIM-Signature header, pre-canonicalized >>>>>>>>>>>>>\n"); + pdkim_quoteprint(CUS sig_hdr, Ustrlen(sig_hdr)); + debug_printf( + "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + } + + /* Relax header if necessary */ + if (sig->canon_headers == PDKIM_CANON_RELAXED) + sig_hdr = pdkim_relax_header(sig_hdr, FALSE); + + DEBUG(D_acl) + { + debug_printf("PDKIM >> Signed DKIM-Signature header, canonicalized (%-7s) >>>>>>>\n", + pdkim_canons[sig->canon_headers]); + pdkim_quoteprint(CUS sig_hdr, Ustrlen(sig_hdr)); + debug_printf( + "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + } + + /* Finalize header hash */ + exim_sha_update(&hhash_ctx, CUS sig_hdr, Ustrlen(sig_hdr)); + exim_sha_finish(&hhash_ctx, &hhash); + + DEBUG(D_acl) + { + debug_printf("PDKIM [%s] Header %s computed: ", + sig->domain, pdkim_hashes[sig->hashtype].dkim_hashname); + pdkim_hexprint(hhash.data, hhash.len); + } + + /* Remember headers block for signing (when the signing library cannot do + incremental) */ + if (ctx->flags & PDKIM_MODE_SIGN) + hdata = exim_dkim_data_append(hdata, US sig_hdr); + + /* SIGNING ---------------------------------------------------------------- */ + if (ctx->flags & PDKIM_MODE_SIGN) + { + hashmethod hm = sig->keytype == KEYTYPE_ED25519 +#if defined(SIGN_OPENSSL) + ? HASH_NULL +#else + ? HASH_SHA2_512 +#endif + : pdkim_hashes[sig->hashtype].exim_hashmethod; + +#ifdef SIGN_HAVE_ED25519 + /* For GCrypt, and for EC, we pass the hash-of-headers to the signing + routine. For anything else we just pass the headers. */ + + if (sig->keytype != KEYTYPE_ED25519) +#endif + { + hhash.data = hdata->s; + hhash.len = hdata->ptr; + } + + if ((*err = exim_dkim_sign(&sctx, hm, &hhash, &sig->sighash))) + { + log_write(0, LOG_MAIN|LOG_PANIC, "signing: %s", *err); + return PDKIM_ERR_RSA_SIGNING; + } + + DEBUG(D_acl) + { + debug_printf( "PDKIM [%s] b computed: ", sig->domain); + pdkim_hexprint(sig->sighash.data, sig->sighash.len); + } + + sig->signature_header = pdkim_create_header(sig, TRUE); + } + + /* VERIFICATION ----------------------------------------------------------- */ + else + { + ev_ctx vctx; + hashmethod hm; + + /* Make sure we have all required signature tags */ + if (!( sig->domain && *sig->domain + && sig->selector && *sig->selector + && sig->headernames && *sig->headernames + && sig->bodyhash.data + && sig->sighash.data + && sig->keytype >= 0 + && sig->hashtype >= 0 + && sig->version + ) ) + { + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_SIGNATURE_ERROR; + + DEBUG(D_acl) debug_printf( + " Error in DKIM-Signature header: tags missing or invalid (%s)\n" + "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n", + !(sig->domain && *sig->domain) ? "d=" + : !(sig->selector && *sig->selector) ? "s=" + : !(sig->headernames && *sig->headernames) ? "h=" + : !sig->bodyhash.data ? "bh=" + : !sig->sighash.data ? "b=" + : sig->keytype < 0 || sig->hashtype < 0 ? "a=" + : "v=" + ); + goto NEXT_VERIFY; + } + + /* Make sure sig uses supported DKIM version (only v1) */ + if (sig->version != 1) + { + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_DKIM_VERSION; + + DEBUG(D_acl) debug_printf( + " Error in DKIM-Signature header: unsupported DKIM version\n" + "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + goto NEXT_VERIFY; + } + + DEBUG(D_acl) + { + debug_printf( "PDKIM [%s] b from mail: ", sig->domain); + pdkim_hexprint(sig->sighash.data, sig->sighash.len); + } + + if (!(sig->pubkey = pdkim_key_from_dns(ctx, sig, &vctx, err))) + { + log_write(0, LOG_MAIN, "PDKIM: %s%s %s%s [failed key import]", + sig->domain ? "d=" : "", sig->domain ? sig->domain : US"", + sig->selector ? "s=" : "", sig->selector ? sig->selector : US""); + goto NEXT_VERIFY; + } + + /* If the pubkey limits to a list of specific hashes, ignore sigs that + do not have the hash part of the sig algorithm matching */ + + if (sig->pubkey->hashes) + { + const uschar * list = sig->pubkey->hashes, * ele; + int sep = ':'; + while ((ele = string_nextinlist(&list, &sep, NULL, 0))) + if (Ustrcmp(ele, pdkim_hashes[sig->hashtype].dkim_hashname) == 0) break; + if (!ele) + { + DEBUG(D_acl) debug_printf("pubkey h=%s vs. sig a=%s_%s\n", + sig->pubkey->hashes, + pdkim_keytypes[sig->keytype], + pdkim_hashes[sig->hashtype].dkim_hashname); + sig->verify_status = PDKIM_VERIFY_FAIL; + sig->verify_ext_status = PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH; + goto NEXT_VERIFY; + } + } + + hm = sig->keytype == KEYTYPE_ED25519 +#if defined(SIGN_OPENSSL) + ? HASH_NULL +#else + ? HASH_SHA2_512 +#endif + : pdkim_hashes[sig->hashtype].exim_hashmethod; + + /* Check the signature */ + + if ((*err = exim_dkim_verify(&vctx, hm, &hhash, &sig->sighash))) + { + DEBUG(D_acl) debug_printf("headers verify: %s\n", *err); + sig->verify_status = PDKIM_VERIFY_FAIL; + sig->verify_ext_status = PDKIM_VERIFY_FAIL_MESSAGE; + goto NEXT_VERIFY; + } + + + /* We have a winner! (if bodyhash was correct earlier) */ + if (sig->verify_status == PDKIM_VERIFY_NONE) + { + sig->verify_status = PDKIM_VERIFY_PASS; + verify_pass = TRUE; + } + +NEXT_VERIFY: + + DEBUG(D_acl) + { + debug_printf("PDKIM [%s] %s signature status: %s", + sig->domain, dkim_sig_to_a_tag(sig), + pdkim_verify_status_str(sig->verify_status)); + if (sig->verify_ext_status > 0) + debug_printf(" (%s)\n", + pdkim_verify_ext_status_str(sig->verify_ext_status)); + else + debug_printf("\n"); + } + } + } + +/* If requested, set return pointer to signature(s) */ +if (return_signatures) + *return_signatures = ctx->sig; + +return ctx->flags & PDKIM_MODE_SIGN || verify_pass + ? PDKIM_OK : PDKIM_FAIL; +} + + +/* -------------------------------------------------------------------------- */ + +DLLEXPORT pdkim_ctx * +pdkim_init_verify(uschar * (*dns_txt_callback)(uschar *), BOOL dot_stuffing) +{ +pdkim_ctx * ctx; + +ctx = store_get(sizeof(pdkim_ctx)); +memset(ctx, 0, sizeof(pdkim_ctx)); + +if (dot_stuffing) ctx->flags = PDKIM_DOT_TERM; +ctx->linebuf = store_get(PDKIM_MAX_BODY_LINE_LEN); +ctx->dns_txt_callback = dns_txt_callback; + +return ctx; +} + + +/* -------------------------------------------------------------------------- */ + +DLLEXPORT pdkim_signature * +pdkim_init_sign(pdkim_ctx * ctx, + uschar * domain, uschar * selector, uschar * privkey, + uschar * hashname, const uschar ** errstr) +{ +int hashtype; +pdkim_signature * sig; + +if (!domain || !selector || !privkey) + return NULL; + +/* Allocate & init one signature struct */ + +sig = store_get(sizeof(pdkim_signature)); +memset(sig, 0, sizeof(pdkim_signature)); + +sig->bodylength = -1; + +sig->domain = string_copy(US domain); +sig->selector = string_copy(US selector); +sig->privkey = string_copy(US privkey); +sig->keytype = -1; + +for (hashtype = 0; hashtype < nelem(pdkim_hashes); hashtype++) + if (Ustrcmp(hashname, pdkim_hashes[hashtype].dkim_hashname) == 0) + { sig->hashtype = hashtype; break; } +if (hashtype >= nelem(pdkim_hashes)) + { + log_write(0, LOG_MAIN|LOG_PANIC, + "PDKIM: unrecognised hashname '%s'", hashname); + return NULL; + } + +DEBUG(D_acl) + { + pdkim_signature s = *sig; + ev_ctx vctx; + + debug_printf("PDKIM (checking verify key)>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n"); + if (!pdkim_key_from_dns(ctx, &s, &vctx, errstr)) + debug_printf("WARNING: bad dkim key in dns\n"); + debug_printf("PDKIM (finished checking verify key)<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + } +return sig; +} + + +/* -------------------------------------------------------------------------- */ + +DLLEXPORT void +pdkim_set_optional(pdkim_signature * sig, + char * sign_headers, + char * identity, + int canon_headers, + int canon_body, + long bodylength, + unsigned long created, + unsigned long expires) +{ +if (identity) + sig->identity = string_copy(US identity); + +sig->sign_headers = string_copy(sign_headers + ? US sign_headers : US PDKIM_DEFAULT_SIGN_HEADERS); + +sig->canon_headers = canon_headers; +sig->canon_body = canon_body; +sig->bodylength = bodylength; +sig->created = created; +sig->expires = expires; + +return; +} + + + +/* Set up a blob for calculating the bodyhash according to the +given needs. Use an existing one if possible, or create a new one. + +Return: hashblob pointer, or NULL on error +*/ +pdkim_bodyhash * +pdkim_set_bodyhash(pdkim_ctx * ctx, int hashtype, int canon_method, + long bodylength) +{ +pdkim_bodyhash * b; + +for (b = ctx->bodyhash; b; b = b->next) + if ( hashtype == b->hashtype + && canon_method == b->canon_method + && bodylength == b->bodylength) + { + DEBUG(D_receive) debug_printf("PDKIM: using existing bodyhash %d/%d/%ld\n", + hashtype, canon_method, bodylength); + return b; + } + +DEBUG(D_receive) debug_printf("PDKIM: new bodyhash %d/%d/%ld\n", + hashtype, canon_method, bodylength); +b = store_get(sizeof(pdkim_bodyhash)); +b->next = ctx->bodyhash; +b->hashtype = hashtype; +b->canon_method = canon_method; +b->bodylength = bodylength; +if (!exim_sha_init(&b->body_hash_ctx, /*XXX hash method: extend for sha512 */ + pdkim_hashes[hashtype].exim_hashmethod)) + { + DEBUG(D_acl) + debug_printf("PDKIM: hash init error, possibly nonhandled hashtype\n"); + return NULL; + } +b->signed_body_bytes = 0; +b->num_buffered_blanklines = 0; +ctx->bodyhash = b; +return b; +} + + +/* Set up a blob for calculating the bodyhash according to the +needs of this signature. Use an existing one if possible, or +create a new one. + +Return: hashblob pointer, or NULL on error (only used as a boolean). +*/ +pdkim_bodyhash * +pdkim_set_sig_bodyhash(pdkim_ctx * ctx, pdkim_signature * sig) +{ +pdkim_bodyhash * b = pdkim_set_bodyhash(ctx, + sig->hashtype, sig->canon_body, sig->bodylength); +sig->calc_body_hash = b; +return b; +} + + +/* -------------------------------------------------------------------------- */ + + +void +pdkim_init_context(pdkim_ctx * ctx, BOOL dot_stuffed, + uschar * (*dns_txt_callback)(uschar *)) +{ +memset(ctx, 0, sizeof(pdkim_ctx)); +ctx->flags = dot_stuffed ? PDKIM_MODE_SIGN | PDKIM_DOT_TERM : PDKIM_MODE_SIGN; +ctx->linebuf = store_get(PDKIM_MAX_BODY_LINE_LEN); +DEBUG(D_acl) ctx->dns_txt_callback = dns_txt_callback; +} + + +void +pdkim_init(void) +{ +exim_dkim_init(); +} + + + +#endif /*DISABLE_DKIM*/ |